FemtoClock® Crystal-to-CML Clock
Generator
8R45252I
Data Sheet
General Description
Features
The 8R45252I is a 3.3V,2.5V CML clock generator designed for
Ethernet applications. The device synthesizes either a 50MHz,
62.5MHz, 100MHz, 125MHz, 156.25MHz, 250MHz or 312.5MHz
clock signal with excellent phase jitter performance. The clock signal
is distributed to two low-skew differential CML outputs. The device is
suitable for driving the reference clocks of Ethernet PHYs. The
device supports 3.3V and 2.5V voltage supply and is packaged in a
small, lead-free (RoHS 6) 32-lead VFQFN package. The extended
temperature range supports telecommunication, wireless
infrastructure and networking end equipment requirements. The
device is a member of the family of High Performance Clock
Solutions from IDT.
• Clock generation of: 50MHz, 62.5MHz, 100MHz, 125MHz,
156.25MHz, 250MHz and 312.5MHz
• Two differential CML clock output pairs
• Crystal interface designed for 25MHz,
18pF parallel resonant crystal
• RMS phase jitter @ 125MHz, using a 25MHz crystal
(1.875MHz – 20MHz): 400fs (typical), 3.3V
Offset
Noise Power
100Hz.................... -102.4 dBc/Hz
1kHz.................... -119.4 dBc/Hz
10kHz................... -124.8 dBc/Hz
100kHz................... -125.7 dBc/Hz
• LVCMOS interface levels for the control inputs
• Full 3.3V and 2.5V supply voltage
• Available in lead-free (RoHS 6) 32 VFQFN package
• -40°C to 85°C ambient operating temperature
Block Diagram
Pin Assignment
XTAL_IN
Q0
nQ0
0
32 31 30 29 28 27 26 25
0
OSC
÷2 (default),
1
2
3
4
5
6
7
8
nQ0
nc
24
23
22
21
VCO
490-680
÷4,
÷5,
Phase
1
Q0
nc
f
REF
Pulldown
VDD
REF_SEL
XTAL_OUT
REF_CLK
REF_SEL
1
nOE
nc
FSEL1
Pulldown
÷20,
÷25 (default)
20 FSEL0
nc
19
nc
nc
nc
Pulldown
Pullup
VDD
nc
18
17
Pulldown, Pulldown
Pulldown
9
10 11 12 13 14 15 16
8R45252I
32 lead VFQFN
5.0mm x 5.0mm x 0.925mm package body
K Package
Top View
©2016 Integrated Device Technology, Inc
1
Revision A January 29, 2016